سؤال يبدو سهلا و لكنه اختلف عيله الكثيرون

[wagih mahmoud]

First I completely agree with Mr. Nashaat.
When we say "a science teacher" , it has only one meaning . But "an English teacher" has two meanings as "English" can describe the language and the nationality . So I think both : "an English teacher" and "a teacher of English" are correct and used.